Content covered:

An NFA is represented formally by a 5-tuple, (Q, Σ, Δ, q_{0}, F), consisting of

1. a finite set of states Q

2. a finite set of input symbols Σ

3. a transition function Δ : Q × Σ → 2^{Q}

4. an initial (or start) state q_{0 }∈ Q

5. a set of states F distinguished as accepting (or final) states F ⊆ Q.

NFA is used in exhuative search or backtacking. No machine can be implemented through NFA.